CN112724275B

CN112724275B - Preparation and application of oak bark polysaccharide

Info

Publication number: CN112724275B
Application number: CN202110122502.1A
Authority: CN
Inventors: 周鸿立; 刘杨; 赵淑庆
Original assignee: Jilin Institute of Chemical Technology
Current assignee: Jilin Institute of Chemical Technology
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2022-07-26
Anticipated expiration: 2041-01-29
Also published as: CN112724275A

Abstract

The invention relates to the field of development of functional foods and medicines, in particular to preparation and application of oak bark polysaccharide with antioxidant and antitumor activities. The method comprises the steps of extracting the oak bark polysaccharide by a water extraction and alcohol precipitation method, purifying by adopting cotton-shaped DEAE, further separating by adopting DEAE-52 column chromatography to obtain the oak bark monomer polysaccharide with four components, and characterizing different components of the oak bark polysaccharide by methods such as UV, IR, HPLC and the like. The polysaccharide with four components has better antioxidant activity through DPPH free radical scavenging experiment, total reducing force measuring experiment and ABTS free radical scavenging experiment; the oak bark polysaccharide obtained by an anti-A549 cell proliferation activity experiment has anti-tumor activity, and is expected to be used as a potential antioxidant and an anti-tumor agent for development of functional foods and medicines.

Description

Preparation and application of oak bark polysaccharide

Technical Field

The invention relates to the field of drug development and functional food, in particular to preparation and application of oak bark polysaccharide.

Background

Mongolian Oak is a plant of the family of the floraceae, also known as the oak tree. Mongolian oak has abundant resources and is mainly distributed in Heilongjiang, Jilin, Liaoning, inner Mongolia, Hebei, Shandong and other provinces. The Mongolian oak bark contains effective components such as flavone and polysaccharide, and has antioxidant, antitumor, and blood sugar lowering effects. In summer, branches of Mongolian oak are generally trimmed and discarded, and a large amount of resources are wasted and the environment is polluted due to large biomass. Therefore, it is of great significance to fully utilize these by-products.

Polysaccharides are formed by condensation and dehydration of a plurality of monosaccharide molecules, are carbohydrate substances with complex and huge molecular structures, and widely exist in nature. It is considered as an important biological response regulator, and has various biological activity functions, such as blood sugar reduction, immune regulation, tumor resistance and the like. Polysaccharides can be generally extracted from plants, but the structures of the polysaccharides are different, the expressed biological activities are also different, and reports about the structure and the application of the oak bark polysaccharide are not found at home and abroad at present.

Antioxidation is biological activity of a plurality of plant effective components, is an important step for preventing aging, and polysaccharides such as dodder polysaccharide, beet polysaccharide and the like have better antioxidation activity in a plurality of literatures. [ antioxidant Activity of Bincholine, KHUDOYBERDIEV, Ilkhomjon, Chengyangxin, Vascula communis ] and study on inhibition of tumor cell proliferation [ J]The proceedings of the university of Industrial science of Henan (Nature science edition), 2020, v.41; No.197(05):79-84.]Experiments show that the clearance rate of the semen cuscutae polysaccharide on DPPH free radicals and hydroxyl free radicals is increased along with the increase of mass concentration, and for DPPH free radicals, I of the semen cuscutae polysaccharide _C50 0.25mg/mL, I of Vc _C50 0.26 mg/mL, which indicates that the semen Cuscutae polysaccharide has strong DPPH free radical scavenging ability, andvc effects are very close. For hydroxyl radical, I of semen Cuscutae polysaccharide _C50 I of Vc 0.36mg/mL _C50 The concentration is 0.29 mg/mL, which shows that the dodder polysaccharide has strong hydroxyl radical scavenging activity. The results show that the semen cuscutae polysaccharide has good antioxidant activity. In order to research the antioxidant activity of the oak bark polysaccharide, the patent researches DPPH free radical scavenging activity, total reducing power and ABTS free radical scavenging activity of the oak bark polysaccharide.

Lung cancer is one of the most rapidly growing malignancies with morbidity and mortality. Wherein non-small cell lung cancer (N SCLC) accounts for 80% of all lung cancer cases. [ CHANCHULIN, KHUDOYEREDIEV, Ilkhomjon, Chengying, LIZAXIN ] research on antioxidant activity and tumor cell proliferation inhibition of semen Cuscutae polysaccharide [ J ] proceedings of the university of Henan industry (Nature science edition), 2020, v.41; No.197(05):79-84 ] experiments show that semen Cuscutae polysaccharide has inhibitory effect on the growth of human lung adenocarcinoma cell A549, human liver cancer cell HepG2 and human pancreatic cancer cell PANC-1, and the inhibitory rate increases with the increase of polysaccharide mass concentration. When the mass concentrations of the cuscuta chinensis polysaccharide are 137.6, 341.7 and 625.4 mu g/mL respectively, the growth inhibition rate of the cuscuta chinensis polysaccharide on A549, HepG2 and PANC-1 can reach 50%. The dodder seed polysaccharide is proved to be capable of effectively inhibiting the proliferation of tumor cells, and the inhibition effects on the expression of different tumor cells are different to a certain extent. In order to research the antitumor activity of the oak bark polysaccharide, the patent researches the anti-A549 cell proliferation activity of the oak bark polysaccharide.

At present, no report is found about the evaluation of the antitumor activity of the oak bark polysaccharide, the research and development of the oak bark polysaccharide have great practical significance, and the patent provides a new thought and a new resource invention content for the research and development of the application of the oak bark polysaccharide to antioxidant and antitumor drugs

Disclosure of Invention

The invention aims to provide a preparation method and application of oak bark polysaccharide

The preparation method of the oak bark polysaccharide is characterized by comprising the following steps of: taking oak bark polysaccharide, and preparing the oak bark crude polysaccharide by adopting a water extraction and alcohol precipitation method; purifying the crude oak bark polysaccharide by adopting pretreated cotton-shaped DEAE cellulose to obtain purified oak bark polysaccharide; and (3) separating the purified oak bark polysaccharide by adopting DEAE-52 cellulose to obtain the oak bark monomer polysaccharide.

Further, the specific method for extracting the oak bark polysaccharide comprises the following steps: refluxing the dried bark powder with 60% ethanol at 90 deg.C for 4 hr twice to remove liposoluble components. And (3) adding the dried residue into boiling water according to the proportion of 1: extracting at a ratio of 20g/ml for 2 h. After two extractions, the supernatants were combined and concentrated to 1/4-1/5 volumes at 55 ℃ under reduced pressure using a rotary evaporator, then precipitated by adding a certain amount of ethanol (95%) until the ethanol content decreased to 80%, and precipitated at 4 ℃ for 12 h. Centrifuging the precipitate in a centrifuge, and freeze drying to obtain final crude polysaccharide of Mongolian oak bark.

Further, the specific method for purifying the oak bark polysaccharide comprises the following steps: 500mg of the crude polysaccharide was dissolved in deionized water and packed into a cotton-like DEAE column (2.6X 30cm) after pretreatment. The column was eluted with 0.6M NaCl solution at a flow rate of 1.0 ml/min. Concentrating the polysaccharide eluate, dialyzing with water, and freeze drying to obtain purified oak bark polysaccharide.

Further, the specific method for separating the oak bark polysaccharide comprises the following steps: 300mg of the purified polysaccharide was dissolved in distilled water and loaded on a DEAE-52 cellulose column (2.6X 30 cm). Elution was carried out with 200ml of distilled water and NaCl solutions of different concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M NaCl) at a flow rate of 1.0ml/min, respectively, and discarded due to the too small fractions of 0.4M and 0.5M. The volume of each polysaccharide collected was 5ml, and four fractions of QMBP-1 (63mg), QMBP-2(8mg), QMBP-3(29mg) and QMBP-4(42mg) were finally obtained.

Further, ultraviolet-visible spectrum and infrared spectrum analysis show that the polysaccharide containing four components contains-OH and-CH ₂ . QMBP-3 and QMBP-4 are 1741.9cm ^-1 There is a weak characteristic peak indicating the presence of uronic acid. Two characteristic absorption peaks are 1627.6cm ^-1 And 1427.1cm ^-1 And (b) represents an asymmetric stretching vibration and a symmetric stretching vibration of COO-. QMBP-3 and QMBP-4 are 1247.9cm ^-1 And 892.9cm ^-1 There are absorption peaks nearby indicating the presence of S = O and C-O-S. In addition, 1000- ^-1 The absorption peak therebetween can be attributed to the extension of C-OH side groupsThe contraction vibration and the C-O-C glycosidic bond vibration are superposed ring vibrations.

Further, the measurement of monosaccharide composition and molecular weight showed that the molecular weights of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 were: 1960kDa, 1036kDa, 922kDa and 919 kDa. Wherein the molar ratio of the QMBP-1 monosaccharide composition is D-mannose: ribose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose-1.62: 0.24: 0.68: 0.32: 1.00: 4.97: 4.88: 35.92; the molar ratio of the QMBP-2 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose-0.62: 0.45: 0.21: 1.00: 0.50: 1.42: 3.31; the molar ratio of the QMBP-3 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.15: 0.23: 0.04: 1.00: 0.15: 0.30: 0.80; the molar ratio of the QMBP-4 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.85: 0.69: 0.07: 1.00: 0.38: 0.79: 1.45.

furthermore, the antioxidant activity of the oak bark polysaccharide is measured, and the result shows that the scavenging effect of the oak bark polysaccharide on DPPH free radicals is increased along with the increase of the concentration in the range of 0.0025-0.01 mg/ml. The DPPH radical scavenging rates at 0.01mg/ml for the crude polysaccharide and ascorbic acid were 56.43% + -1.8% and 80.83% + -3.1, respectively. Ascorbic acid has a greater DPPH scavenging activity than the crude polysaccharide at the same concentration (0.01 mg/ml). IC of crude polysaccharide and ascorbic acid ₅₀ 8.7. + -. 0.25. mu.g/ml and 6.6. + -. 0.16. mu.g/ml, respectively.

Further, the crude polysaccharide has a strong reducing power. The absorption of the crude polysaccharide increased from 0.314. + -. 0.65 to 0.997. + -. 0.62 with an increase in concentration from 0.05 to 0.25 mg/ml. At 0.2mg/ml, the absorbance of the crude polysaccharide was 0.894. + -. 0.57, which was approximately equal to that of ascorbic acid (absorbance: 0.903. + -. 0.29). IC of crude polysaccharide and ascorbic acid ₅₀ 0.09 + -0.36 mg/ml and 0.08 + -0.23 μ g/ml, respectively.

Further, the clearance rate of crude polysaccharide concentration in the range of 0.001-0.009 mg/ml to ABTSThe scavenging effect by radicals increases with increasing concentration and approaches ascorbic acid. IC of crude polysaccharide and ascorbic acid ₅₀ 8.3 +/-0.16 mu g/ml and 6.3 +/-0.09 mu g/ml respectively.

Further, the results of the determination of the anti-A549 cell proliferation activity of the oak bark polysaccharide show that the four components have obvious inhibition effect on the A549 cell proliferation and are dose-dependent. Within 24h, when the maximum inhibition concentration is 0.4mg/ml, the QMBP-1 has the best inhibition effect, and the inhibition rate is 37.5%; secondly, QMBP-2 is adopted, and the inhibition rate is 30.0 percent; the inhibition rate of QMBP-4 is 22.5 percent; the inhibition rate of QMBP-3 was 15.0%. The QMBP-1 has the best inhibition effect when the maximum inhibition concentration is 0.4mg/ml within 48h, and the inhibition rate is 40 percent (p is less than 0.001); the second is QMBP-3, the inhibition rate is 20.0%, and the inhibition rates of QMBP-4 and QMBP-2 are reduced to about 10% compared with 24 h. In conclusion, QMBP-1 and QMBP-3 have dose-dependent and time-dependent anti-lung cancer activity in vitro, while QMBP-2 and QMBP-4 exert in vitro anti-cancer activity only in a dose-dependent, but not time-dependent manner.

Compared with the prior art, the method has outstanding substantive characteristics and remarkable progress, and particularly, the method prepares the oak bark polysaccharide and researches the chemical structure of the oak bark polysaccharide for the first time; the invention also provides the first research for exploring the Mongolian oak bark polysaccharide component in the anticancer cells, and the provided data shows that the Mongolian oak bark polysaccharide has higher anticancer potential. The invention applies the oak bark polysaccharide to the development and research of antioxidant and antitumor drugs, and develops a new idea of the oak bark extract in the aspects of research and development of foods, health-care products and new antitumor drugs.

Drawings

FIG. 1 is a DEAE-52 cellulose fast flow chromatogram of QMBP

FIG. 2 shows the UV spectrum of QMBP

FIG. 3 is an infrared spectrum of QMBP

FIG. 4 is the FT-IR spectral second derivative of QMBP

FIG. 5 is an HPLC chromatogram of the hydrolysates of monosaccharide standards (A), QMBP-1(B), QMBP-2(C), QMBP-3(D) and QMBP-4 (E). Man: mannose, Rib: ribose, Rha: rhamnose, GluA: glucuronic acid, GalA: galacturonic acid, Glu: glucose, Gal: galactose, Xylose: xylose, Ara: arabinose, Fuc: fucose sugar

FIG. 6 shows the antioxidant activity of QMBP. DPPH radical scavenging activity (A), reducing power (B), ABTS + radical scavenging activity (C). Statistical analysis was performed on IC50 values for different radicals. Data are expressed as mean ± SD (n = 3). The symbol indicates that the difference is statistically significant, P < 0.01 vs VC (D)

FIG. 7 is a graph of the effect of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 on the viability of A549 cells at different concentrations and at different time points. 7(A) shows the cell viability after 24h treatment with different concentrations of QMBP-1, QMBP-2, QMBP-3 and QMBP-4. 7(B) shows 48 h.

Detailed Description

The technical solution of the present invention is further described in detail by the following embodiments.

Extraction of oak bark polysaccharide

The dried bark powder was refluxed with 60% ethanol at 90 deg.C for 4h twice to remove ethanol soluble components. And (3) adding the dried residue into boiling water according to the proportion of 1: extracting at a ratio of 20g/ml for 2 h. After two extractions, the supernatants were combined and concentrated to 1/4-1/5 volumes at 55 ℃ under reduced pressure using a rotary evaporator, then precipitated by adding a certain amount of ethanol (95%) until the ethanol content decreased to 80%, and precipitated at 4 ℃ for 12 h. Separating the precipitate with centrifuge, and lyophilizing to obtain final crude polysaccharide of Mongolian oak bark.

Purification of oak bark crude polysaccharide

Soaking cotton DEAE in distilled water to remove impurities, soaking in 0.5M HCl solution for 1-2h, washing with deionized water to neutral pH, and discharging. Soaking in 0.5M NaOH solution for 1-2 hr, and washing with deionized water to neutral pH. 500mg of the crude polysaccharide was dissolved in deionized water and packed into a cotton DEAE column (2.6X 30 cm). The column was eluted with 0.6M NaCl solution at a flow rate of 1.0 ml/min. Concentrating the polysaccharide eluate, dialyzing with water, and lyophilizing.

The total carbohydrate content of the crude polysaccharide was 37.32% + -1.53% and the carbohydrate content increased to 68.42% + -3.25 after purification. In addition, the protein content of the crude polysaccharide was 6.14. + -. 1.07%, and the purified polysaccharide was 1.43. + -. 0.26%. The results show that the protein content of the polysaccharide is reduced. The polysaccharide recovery rate, the deproteinization rate and the decolorization rate are respectively 54.82 +/-1.24%, 79.06 +/-2.31% and 87.12 +/-1.51%. After purified by cotton DEAE, the residual quantity of protein and pigment is effectively reduced.

Separation of oak bark crude polysaccharide

300mg of the purified polysaccharide was dissolved in distilled water and loaded on a DEAE-52 cellulose column (2.6X 30 cm). The column was eluted with 200ml of distilled water and NaCl solutions of different concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M NaCl) at a flow rate of 1.0 ml/min. The 0.4M and 0.5M fractions were discarded because they were too small. The volume of each polysaccharide collected was 5ml, and the detection was carried out by the phenol-sulfuric acid method. Four-component polysaccharides QMBP-1 (63mg), QMBP-2(8mg), QMBP-3(29mg) and QMBP-4(42mg) were obtained, and the polysaccharides were concentrated, dialyzed against water, lyophilized, and further studied. The polysaccharide, uronic acid and protein content of the four components are shown in table 1.

TABLE 1 polysaccharide, uronic acid and protein content of the four components

Content (%)	QMBP-1	QMBP-2	QMBP-3	QMBP-4
					Polysaccharides	91.32±0.29	52.54±0.17	53.72±0.16	60.41±0.17
Uronic acid	5.21±0.21	15.00±0.25	31.92±0.21	35.57±0.25
					Protein	0.35±0.16	0.84±0.12	0.55±0.12	0.69±0.29

Ultraviolet-visible and infrared spectroscopic analysis

Functional groups of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 were identified using FT-IR spectrophotometers. The polysaccharide of each component was thoroughly mixed with KBr powder, ground, and tableted. The infrared spectrum scanning range is from 4000 to 400cm ^-1 . In addition, each FT-IR spectrum was smoothed by a smoothing factor of 13, and the second derivative of the spectrum was obtained using the OMN IC8.0Savitsky-Golay derivative.

The ultraviolet and infrared spectra of the four components are shown in fig. 2 and 3. The weak absorptions observed with the UV spectrum (FIG. 2) at 280nm for QMBP-1, QMBP-2, QMBP-3 and QMBP-4 indicate trace amounts of protein, which may also be due to the presence of glycoproteins in the four components. The infrared spectrum (FIG. 3) of the four polysaccharides was 3410.4cm ^-1 The left and right show a broad and strong absorption peak, which is attributed to the stretching vibration of-OH, and the peak is 2925.3 ^-1 Is due to-CH ₂ And (5) stretching and vibrating. QMBP-3 and QMBP-4 are 1741.9cm ^-1 There is a weak characteristic peak indicating the presence of uronic acid. Two characteristic absorption peaks are 1627.6cm ^-1 And 1427.1cm ^-1 And (b) represents an asymmetric stretching vibration and a symmetric stretching vibration of COO-. QMBP-3 and QMBP-4 at 1247.9cm ^-1 And 892.9cm ^-1 There are absorption peaks nearby indicating the presence of S = O and C-O-S. In addition, 1000-1200cm ^-1 The absorption peak therebetween can be attributed to the ring vibration overlapping with the stretching vibration of the C-OH side group and the vibration of the C-O-C glycosidic bond.

Second order derivatives of the FT-IR spectra, QMBP-1 and QMBP-2, shown in FIG. 4 are at 1731.7cm ^-1 And 1743.3cm ^-1 There is an absorption peak for uronic acid. Only one shoulder is visible in the infrared spectrum. From the infrared spectrum, it can be seen that the uronic acid content of QMBP-3 and QMBP-4 is higher than that of QMBP-1 and QMBP-2, which is consistent with the test results of uronic acid ion concentration. The combination of the infrared spectrum and the second derivative spectrum shows that the beta-glucopyranoside bond is 860cm ^-1 There is a characteristic absorption. The second derivative of the infrared spectrum can improve the resolution of a one-dimensional infrared spectrogram, the infrared spectrum of each fraction is not completely the same as the second derivative spectrum, and the difference of the characteristic peaks proves the structural difference of the four components.

Determination of monosaccharide composition and molecular weight

Every 2mg of sample was completely hydrolyzed to monosaccharides in an oven at 120 ℃ with trifluoroacetic acid (2M, 2ml) in a hydrothermal reactor. After completion of the hydrolysis, the solution is concentrated to dryness (<45 ℃) and the residue is then dissolved in 3ml of methanol and evaporated to dryness. This procedure was repeated five times to completely remove excess TFA. The dried hydrolysate was labeled with PMP and 200. mu.L of L0.3MNaOH, 200. mu.L of 0.5M PMP-CH was added ₃ OH solution, the mixture was reacted at 70 ℃ for 60 min. Subsequently, the reaction product was neutralized with 200. mu.L of 0.3M HCl solution and extracted three times with 1ml of chloroform. The aqueous layer containing the PMP-labeled derivative was then filtered through a 0.45 μm membrane and subjected to high performance liquid chromatography detection by Ultimate3000, equipped with a Supersil ODS2 column (5 μm, 4.6X 250mm2) and an Ultimate3000 diode array detector (DAD, Thermo). The chromatographic conditions were set as follows: a mobile phase comprising PBS (pH6.8) and acetonitrile (82: 18 v/v); the flow rate is 0.8 ml/min; the column temperature is 30 ℃; the detector wavelength was 245 nm; the running rate was 85 min. Using different monosaccharides as standard (mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, arabinose, fucoidinSugar) and the corresponding peak area and response factor are used to calculate the content of each sugar.

Molecular weight was determined using a high performance size exclusion chromatograph associated with a refractive index detector. 20 μ L of the sample solution (2.0mg/ml) was passed through a 0.45 μm filter, and the Shodex sugar was injected onto a KS-804 column (8.0 mm. times.300 mm) and analyzed by HPLC equipped with a Refractive Index Detector (RID). Data processing was recorded on an N2000GPC chromatography workstation. The chromatographic conditions are as follows: an ultrapure water mobile phase; the flow rate is 1.0 ml/min; the column temperature is 50 ℃; RID temperature 35 ℃; the running speed was 30 min. Calibration curves were established using dextran standards of different molecular weights.

Figure 5 shows that these four components are heteropolysaccharides. As shown in Table 2, the molar ratio of the QMBP-1 monosaccharide composition is D-mannose: ribose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose 1.62: 0.24: 0.68: 0.32: 1.00: 4.97: 4.88: 35.92; the molar ratio of the QMBP-2 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose-0.62: 0.45: 0.21: 1.00: 0.50: 1.42: 3.31; the molar ratio of the QMBP-3 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.15: 0.23: 0.04: 1.00: 0.15: 0.30: 0.80; the molar ratio of the QMBP-4 monosaccharide composition is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.85: 0.69: 0.07: 1.00: 0.38: 0.79: 1.45. further, the molecular weights of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 are: 1960kDa, 1036kDa, 922kDa and 919 kDa.

TABLE 2 monosaccharide composition (molar ratio) and molecular weight (kDa)

Oak bark polysaccharide pharmacodynamic test

The following experiment is carried out on the oak bark polysaccharide to verify the pesticide effect of the oak bark polysaccharide provided by the invention.

Determination of antioxidant activity of oak bark polysaccharide

Experiment for eliminating DPPH free radical by oak bark polysaccharide

2ml of QMBP samples at different concentrations (2.5, 3.75, 5, 7.5, 10. mu.g/ml) were mixed with 2ml of 0.2M DPPH-C ₂ H ₅ And (4) mixing the OH solution. The mixture was shaken vigorously and allowed to react dark at room temperature for 30min, and the absorbance of the reduced DPPH was measured at 517nm with a UV-visible spectrophotometer. Ethanol was used as a negative control and ascorbic acid was used as a positive control at concentrations of 1.25, 2.5, 5, 7.5, 10. mu.g/ml. All tests were done in triplicate. The formula for calculating DPPH free radical scavenging activity is as follows:

DPPH radical scavenging activity (%) = [ 1- (a) ₁ −A ₀ )/A ₂ ] ×100% (1)

A ₀ Absorbance of the sample only (sample without DPPH solution), A ₁ Is the absorbance of a sample containing a DPPH radical solution, A ₂ Is the absorbance of the control (without DPPH solution).

FIG. 6 (a) shows the DPPH radical scavenging ability of crude polysaccharide with ascorbic acid as a positive control. The crude polysaccharide had moderate antioxidant activity over the tested concentration range, whereas ascorbic acid had a strong ability to scavenge DPPH free radicals. Within the range of 0.0025-0.01mg/ml, the scavenging effect of the crude polysaccharide is increased along with the increase of the concentration, and DPPH free radicals can be better scavenged. The DPPH radical scavenging rates at 0.01mg/ml for the crude polysaccharide and ascorbic acid were 56.43% + -1.8% and 80.83% + -3.1, respectively. Ascorbic acid has a greater DPPH scavenging activity than the crude polysaccharide at the same concentration (0.01 mg/ml). IC of crude polysaccharide and ascorbic acid ₅₀ 8.7. + -. 0.25. mu.g/ml and 6.6. + -. 0.16. mu.g/ml, respectively.

Experiment of reducing power

1ml of the sample at concentrations of 0.05, 0.1, 0.15, 0.20 and 0.25mg/ml respectively was mixed with 2.5ml of 0.2M sodium phosphate buffer (sodium phosphate buffer: (B))pH6.6) and 2.5ml of potassium ferricyanide (1%) and the mixture is reacted at 50 ℃ for 20 min. The reaction was stopped by adding 2.5ml of TCA solution (10%) and the mixture was centrifuged at 3000rpm for 10 min. 2.5ml of the supernatant was mixed with 2.5ml of distilled water and 0.5ml of a solution of ferric chloride (0.1%) at 700nmThe blank absorbance was measured. Distilled water was used as a blank control, and ascorbic acid was used as a positive control. Its higher absorbance indicates higher reducing power.

The existence of antioxidant components in the tested sample can lead Fe ³⁺ Reduction of ferricyanide compounds to Fe ²⁺ In the ferrous form. The change in color reflects the reducing power of the antioxidant. Higher absorbance values indicate stronger reducing power. Fig. 6(b) depicts the reducing power of the sample and ascorbic acid, and the crude polysaccharide showed significant reducing power at each concentration point. The absorption of the crude polysaccharide increased from 0.314. + -. 0.65 to 0.997. + -. 0.62 with an increase in concentration from 0.05 to 0.25 mg/ml. At 0.2mg/ml, the absorbance of the crude polysaccharide was 0.894. + -. 0.57, which was approximately equal to that of ascorbic acid (absorbance: 0.903. + -. 0.29). IC of crude polysaccharide and ascorbic acid ₅₀ 0.09 + -0.36 mg/ml and 0.08 + -0.23 μ g/ml respectively. The data indicate that the strong reducing power of the crude polysaccharide plays an important role in oxidation resistance.

Experiment for eliminating ABTS free radical by oak bark polysaccharide

Mixing with 88 mu L K ₂ S ₂ O ₈ (2.45 mmol/L) was injected into ABTS (7 mmol/L) to prepare an ABTS solution. And reacting for 12-16 h in the dark at room temperature. The resulting mixture was then further diluted with phosphate buffer (pH =7.4) to bring the absorbance of the solution at 734nm to 0.70 ± 0.02. 2ml of an aqueous polysaccharide solution having a concentration of 2.5 to 15. mu.g/ml was added to the diluted solution, and mixed with ABTS (2.0 ml). The mixed solution was reacted for 5min, and then the absorbance at 734nm was measured. The formula for calculating the ABTS free radical scavenging activity is as follows:

ABTS radical scavenging activity (%) =

×100% (2）

Ai is the absorbance of the active product, Aj is the absorbance of the blank reagent, A ₀ Is the absorbance of the blank sample.

As shown in FIG. 6 (c), the clearance rate of crude polysaccharide concentration in the range of 0.001-0.009 mg/ml is close to that of ascorbic acid. IC of crude polysaccharide and ascorbic acid ₅₀ Respectively 8.3 +/-0.16 mu g/ml and 6.3 +/-0.09 mu g/ml。

Antioxidant activity research shows that the oak bark polysaccharide has high DPPH free radical scavenging capacity, reducing power and ABTS free radical scavenging capacity. According to the ion concentration experiment, the total content of the carbohydrate and the protein in the crude polysaccharide is 37.32% + -1.53% and 6.14 + -1.07 respectively. It can be seen that total carbohydrate is the main component of the crude polysaccharide, playing an important role in oxidation resistance. Therefore, the oak bark polysaccharide has stronger antioxidant activity.

Assay for inhibiting A549 cell proliferation activity

Cells and cell culture

At 37 deg.C, 5% CO ₂ A549 cells were cultured in RPMI medium supplemented with 10% (v/v) FBS and 1% (v/v) antibiotic solution. Stock solutions of 100mg/ml QMBP-1, QMBP-2, QMBP-3 and QMBP-4 were prepared, mixed with DMSO, and stored at-20 ℃ in the dark until use. Further dilutions were made in RPMI medium containing 10% FBS before the cell reaction was initiated. The final concentrations and reaction times with the samples are shown in each figure.

Cell viability and proliferation

The MTT method is used to determine the effect of purified polysaccharide on the vitality of A549 cells. Cells grown in medium were treated with purified polysaccharide at a concentration of 50-400. mu.g/ml in 96-well plates, and control cells were grown in medium without purified polysaccharide. MTT (20. mu.L, 5mg/ml) was added after 24 or 48 hours of cell reaction, and after 4 hours of reaction, the medium was aspirated, 150. mu.L MSO was added to each well, and the absorbance was measured at 570nm in a 96-well microplate reader. All experiments were performed 3 times.

Statistical analysis

One-way analysis of variance and least significant difference test (LSD) using the SPSS17.0 program were used to determine significance between groups,pvalues less than 0.05 are considered statistically significant.

MTT experiments show that compared with a blank group, the four components have obvious inhibition effect on A549 cell proliferation and are dose-dependent. FIG. 7(a) (b) shows that cells were treated with 0.05, 0.1, 0.2 and 0.4mg/ml QMBP-1, QMBP-2, QMBP-3 and QMBP-4 for 24h and 48h, respectively. As shown in FIG. 7(a), QMBP-1 showed the best inhibitory effect at the maximum inhibitory concentration of 0.4mg/ml within 24 hours, with an inhibitory rate of 37.5%; secondly, QMBP-2 is adopted, and the inhibition rate is 30.0 percent; the inhibition rate of QMBP-4 is 22.5 percent; the inhibition rate of QMBP-3 was 15.0%.

As shown in FIG. 7(b), the inhibitory effect of QMBP-1 was the best at the maximum inhibitory concentration of 0.4mg/ml within 48 hours, with an inhibitory rate of 40% (p < 0.001); the second is QMBP-3, the inhibition rate is 20.0%, and the inhibition rates of QMBP-4 and QMBP-2 are reduced to about 10% compared with 24 h.

Taken together, QMBP-1 and QMBP-3 have both dose-and time-dependent anti-lung cancer activity in vitro, while QMBP-2 and QMBP-4 exert anti-lung cancer activity in vitro only in a dose-dependent, but not time-dependent manner. The oak bark polysaccharide can be a cell cycle specific antitumor drug, can inhibit the growth of tumor cells at a certain stage of the cell cycle, and can inhibit the cell cycle of lung cancer by the four components at different stages. As QMBP-1 obviously reduces the cell viability in concentration and time, the inhibition effect of QMBP-1 on A549 lung cancer cells is better than that of QMBP-3.

The research shows that the four components of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 have rich monosaccharide compositions and larger molecular weight distribution, and the QMBP-1 has obvious inhibition effect on the lung cancer A549 cell proliferation. The research is also a research for exploring the first time of the Mongolian oak bark polysaccharide component in the anticancer cells, and the provided data shows that the Mongolian oak bark polysaccharide has higher anticancer potential, so that a new strategy is provided for treating the lung cancer.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A preparation method of oak bark polysaccharide is characterized in that the molecular weights of four prepared polysaccharides of QMBP-1, QMBP-2, QMBP-3 and QMBP-4 are 1960kDa, 1036kDa, 922kDa and 919kDa respectively; the preparation process of the polysaccharide comprises the following steps:

(1) refluxing the dried bark powder with 60% ethanol at 90 deg.C for 4 hr, and refluxing twice to remove fat soluble components; and (3) adding the dried residue into boiling water according to the proportion of 1: extracting at a ratio of 20g/ml for 2 h; after two extractions, the supernatants are combined and concentrated to 1/4-1/5 volume by a rotary evaporator under 55 ℃ and reduced pressure, and then a certain amount of 95% ethanol is added for precipitation until the ethanol content is reduced to 80%, and the precipitation is carried out for 12 hours at 4 ℃; centrifuging the precipitate in a centrifuge, and freeze drying to obtain crude polysaccharide of Mongolian oak bark; the content of crude polysaccharide is 37.32% + -1.53%, and the protein content of crude polysaccharide is 6.14 + -1.07%;

(2) dissolving 500mg of crude polysaccharide in deionized water, and loading into pretreated cotton-like DEAE column of 2.6 × 30 cm; eluting with 0.6M NaCl solution at 1.0 ml/min; concentrating the polysaccharide eluate, dialyzing with water, and lyophilizing to obtain purified oak bark polysaccharide; the content of the purified protein obtained by extraction is increased to 68.42 +/-3.25, and the protein content is reduced to 1.43 +/-0.26%;

(3) dissolving 300mg purified polysaccharide in distilled water, loading on 2.6 × 30cm DEAE-52 cellulose column, eluting with 200ml distilled water and 0.1, 0.2, 0.3, 0.4 and 0.5M NaCl solution respectively at flow rate of 1.0ml/min, discarding due to too small fraction of 0.4M and 0.5M; collecting each polysaccharide with volume of 5ml, detecting with phenol-sulfuric acid method to obtain 63mg of QMBP-1, 8mg of QMBP-2, 29mg of QMBP-3 and 42mg of QMBP-4, concentrating the polysaccharide, dialyzing with water, and freeze drying;

(4) the molar ratios of monosaccharide compositions of the prepared polysaccharides with the four components are respectively as follows: QMBP-1 is D-mannose: ribose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose 1.62: 0.24: 0.68: 0.32: 1.00: 4.97: 4.88: 35.92; QMBP-2 is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: xylose-0.62: 0.45: 0.21: 1.00: 0.50: 1.42: 3.31; QMBP-3 is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.15: 0.23: 0.04: 1.00: 0.15: 0.30: 0.80; QMBP-4 is D-mannose: rhamnose: d-glucuronic acid: d-galacturonic acid: d-glucose: d-galactose: arabinose 0.85: 0.69: 0.07: 1.00: 0.38: 0.79: 1.45 of;

(5) IC of prepared oak bark crude polysaccharide for eliminating DPPH free radical ₅₀ 8.7 plus or minus 0.25 mu g/ml; IC of total reducing power ₅₀ Is 0.09 +/-0.36 mg/ml; IC for clearance of ABTS free radicals ₅₀ 8.3 +/-0.16 mu g/ml, which indicates that the antioxidant has better antioxidant activity;

(6) the prepared four oak bark polysaccharides have certain antitumor activity on A549 cell proliferation activity experiments, wherein QMBP-1 has obvious activity, and the maximum inhibition rate within 48h is 40% when the maximum inhibition concentration is 0.4 mg/ml.

2. The method for preparing oak bark polysaccharide of claim 1, wherein the four component polysaccharides comprise-OH, -CH, by UV-visible and IR spectroscopy ₂ COO-and uronic acid; in QMBP-3 and QMBP-4, S = O, C-O-S, C-OH and C-O-C are additionally present.